As a widely used illumination technology, the LED light-emitting technology has the advantages of high luminous intensity, long lifespan and high efficiency with low energy consumption. An illumination device or illumination module using an LED light source usually needs to have a good light distribution. Thus, the lens for an LED light source is often used in such illumination device or illumination module, to finally form the expected light distribution of emergent light by means of optical performance of the lens. However, in practical applications, light emerging from the lens usually forms stray light that is different from the main emergent light, and such stray light usually affects the actual optical performance of the illumination device or illumination module.
One related art solution proposes to use non-transparent printing—, which is disposed on a side surface of the lens of the illumination device, so that light, particularly stray light, from the light source of the lens will be blocked by the printing on the transparent side surface, and therefore the stray light cannot emerge to affect the main emergent light emerging from the lens. According to this design, although stray light can be blocked, the technology of forming printing on the transparent outer surface is relatively complicated, and the printing cannot withstand long-term influences from the outside, for example, friction, which will lead to deterioration or even loss of the light blocking effect. In addition, another related art solution proposes to use a non-transparent cover, dispose the cover outside the illumination device and make it abut against the outer surface of the illumination device, thereby achieving the effect of blocking stray light. However, the additional cover increases the cost of the illumination device.